Limit Switch Device for an Actuator

ABSTRACT

A limit switch device for an actuator comprises a brake rod, a mounting frame and two switches. The brake rod is axially movable with respect to the mounting frame. The two switches are mounted on the mounting frame and located in the axial direction of the brake rod and are connected to the actuator, respectively. When the actuator moves to the end of its travel, it will drive the brake rod to move and switch on one of the switches, and the switch will stop the actuator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an actuator, and more particularly to a limit switch device for an actuator.

2. Description of the Prior Art

Currently, there are many types of actuators on the market, one of actuators is provided with a power source on its outer housing, and a transmission shaft is inserted through the housing and is driven by the power source to reciprocate within the outer housing along the axial direction of the transmission shaft. However, the actuator is unable to know if the transmission shaft has moved to the end of its travel. Therefore, it will cause damage to the actuator if the transmission shaft has reached its maximum travel but the actuator doesn't know and still keeps moving.

A new limit switch device was developed to solve the abovementioned problem, as shown in FIG. 1. The limit switch device is disposed in an actuator A and includes two switches 10 connected to the actuator A. the two switches 10 are located at one side of a transmission shaft A1 of the actuator A and at both ends of the travel of the transmission shaft A1, respectively. A limit block A2 is disposed on the transmission shaft A1 of the actuator A and located between the two switches 10. When the transmission shaft A1 reaches its maximum travel, the limit block A2 will presses one of the switches 10, and then the switch 10 will stop the actuator A, thus achieving the purpose of controlling the travel limit of the actuator A.

However, such a limit switch device should be disposed in the actuator A and must be located at both ends of the travel of the transmission shaft A1. Therefore, the control and connection structure between the switches 10 and the actuator A is relatively complicated and needs to be improved.

Hence, another limit switch device appears on the market, as shown in FIG. 2A, and comprises a mounting frame 21, a first brake rod 22, a second brake rod 23, a first switch 24 and a second switch 25. The first and second brake rods 22, 23 are parallelly inserted on the mounting frame 21, and the first and second switches 24, are mounted in the mounting frame 21 and located correspondingly to the first and second switches 24, 25. A first spring 26 is mounted on the first brake rod 22 and pushes the first brake rod 22 toward the first switch 24 so as to maintain the first switch 24 in an “On” state. On the other end of the first brake rod 22 opposite the first switch 24 is fixed a limit block 27. A second spring 28 is mounted on the second brake rod 23 and pushes the second brake rod 23 in a direction opposite the second switch 25, and the second switch 25 is kept in an “off” state. The limit block A2 of the transmission shaft A1 of the actuator A is mounted on the first brake rod 22.

When the transmission shaft A1 moves, it drives the limit block A2 to move along the first brake rod 22, and when the limit block A2 moves to the limit block 27 of the first brake rod 22, it starts to pull the first brake rod 22 to move, as shown in FIG. 2B, accordingly the first brake rod 22 stops pressing and moves away from the first switch 24, so that the first switch 24 is changed into an “off” state. When the first and second switches 24, 25 are both changed into “off” state, the actuator A is controlled to stop operation. Moreover, when the limit block A2 moves and presses the second brake rod 23, as shown in FIG. 2 c, the second brake rod 23 moves toward and presses the second switch 25, and accordingly the second switched 25 is switched on. When the first and second switches 24, 25 are all switched on, the actuator A will be controlled to start operation.

This limit switch device has solved the shortcoming caused by the both ends of the transmission shaft A of the previous conventional limit switch device, however, it must use two brake rods, therefore, its structure and operation are still complicated and need to be improved.

The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a limit switch device for an actuator capable of simplifying the control of the travel of the actuator.

The limit switch device for an actuator in accordance with the present invention comprises two switches and a brake rod inserted in a mounting frame. The brake rod is connected to the transmission shaft of the actuator, the two switches are connected to the actuator, and the brake rod axially reciprocates on the mounting frame. A protruding block is disposed on the brake rod, and the two switches are juxtaposed on the mounting frame and located in the axial direction of the brake rod and arranged at both sides of the protrudes block.

When the actuator moves, its transmission shaft also moves in the axial direction of the brake rod, and when the transmission shaft moves to the end of its travel, it will drive the brake rod to move. When the protruding block on the brake rod presses one of the switches, the switch will stop the actuator.

Since the present invention only needs a single brake rod to control the travel of the transmission shaft, it is advanced as compared with the conventional structure using two brake rods.

In addition, the brake rod is further provided with a first flange, a second flange, a stop block and two springs, the two spring are located at both sides of the first flange and push against the mounting frame for elastically pushing the transmission shaft back to its original position. The second flange and the stop block are located outside the mounting frame, the transmission shaft of the actuator has a limit block mounted on the brake rod and located between the second flange and the stop block. When the transmission shaft moves to the end of its travel, the limit block will push the second flange or the stop block to drive the brake rod to move, thus stopping the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a conventional limit switch device for an actuator;

FIG. 2A is a perspective view of another conventional limit switch device for an actuator;

FIG. 2B is a perspective view of the conventional limit switch device of FIG. 2A that stops the actuator;

FIG. 2C is another perspective view of the conventional limit switch device of FIG. 2A that stops the actuator;

FIG. 3 is a perspective view of a limit switch device for an actuator in accordance with the present invention;

FIG. 4A is a perspective view of showing how the limit switch device in accordance with the present invention stops the actuator;

FIG. 4B is another perspective view of showing how the limit switch device in accordance with the present invention stops the actuator; and

FIG. 5 is a perspective view in accordance with the present invention of showing that the stop block is screwed on the brake rod.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be more clear from the following description when viewed together with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiment in accordance with the present invention.

Referring to FIG. 3, a limit switch device for an actuator in accordance with a preferred embodiment of the present invention comprises: a mounting frame 30, a brake rod 40, a first switch 50 and a second switch 60.

The mounting frame 30 is sequentially provided with a first stop portion 31, a second stop portion 32 and a third stop portion 33.

The brake rod 40 has one end inserted in the mounting frame 30 through the second and third stop portions 32, 33 thereof, and from this end of the brake rod 40 are sequentially disposed a protruding block 41, a first flange 42 and a second flange 43. The protruding block 41 is located between the first and second stop portions 31, 32, the first flange 42 is located between the second and third stop portions 32, 33, and the second flange 43 is located outside the third stop portion 33. A first spring 44 and a second spring 45 are mounted on the brake rod 40, the first spring 44 is located between the first flange 42 and the second stop portion 32, and the second spring 45 is located between the first flange 42 and the third stop portion 33. On the other end of the brake rod 40 is disposed a stop block 46. A limit block A2 of the transmission shaft of the actuator is mounted on the brake rod 40 and located between the second flange 43 and the stop block 46.

The first and second switches 50, 60 are disposed on the mounting frame 30 and connected to the actuator, respectively. The first and second switches 50, 60 are located between the first and second stop portions 31, 32 and are juxtaposed along the axial direction of the brake rod 40. The first switch 50 is located close to the first stop portion 31 and the second switch 60 is located close to the second stop portion 32, and they are located at both sides of the protruding block 41.

When the transmission shaft of the actuator performs linear displacement, the limit block A2 on the transmission shaft simultaneously moves along the brake rod 40. And when the limit block A2 moves to the stop block 46 of the brake rod 40, it will push the stop block 46 and drive the brake rod 40 to move, as shown in FIG. 4A. At this moment, the first flange 42 of the brake rod 40 will compress the second spring 45. And when the protruding block 41 presses the second switch 60, the second switch 60 will stop the actuator.

When the limit block A2 moves to the second flange 43 of the brake rod 40 and pushes the brake rod 40 to move, as shown in FIG. 4B, the first flange 42 of the brake rod 40 will compress the first spring 44, meanwhile, the protruding block 41 will press the first switch 50, and thus the first switch 50 stops the actuator.

When the limit block 42 moves away from the second flange 43 or the stop block 46, the first and second springs 44, 45 will push the brake rod 40 to its original position.

In addition, the stop block 46 of the brake rod 40 can also be screwed on the brake rod 40, as shown FIG. 5, so that the moving distance of the transmission shaft of the actuator can be adjusted by adjusting the position of the stop block 46 on the brake rod 40.

To summarize, the limit switch device for an actuator in accordance with the present invention comprises a brake rod, a mounting frame and two switches. The brake rod is axially movable with respect to the mounting frame. The two switches are mounted on the mounting frame and located in the axial direction of the brake rod and are connected to the actuator, respectively. When the actuator moves to the end of its travel, it will drive the brake rod to move and switch on one of the switches, and the switch will stop the actuator.

While we have shown and described various embodiments in accordance with the present invention, it is clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention. 

1. A limit switch device for an actuator comprising a brake rod, a mounting frame and two switches, the two switches being mounted on the mounting frame and connected to the actuator, the brake rod being moveably inserted in the mounting frame and connected to a transmission shaft of the actuator; characterized in that: the brake rod axially reciprocates on the mounting frame, the two switches are juxtaposed on the mounting frame and located in an axial direction of the brake rod, a protruding block is disposed on the brake rod and located between the two switches, the brake rod is driven by the transmission shaft of the actuator to move axially, when the protruding block of the brake rod presses one of the switches, the switch will stop the actuator.
 2. The limit switch device for an actuator as claimed in claim 1, wherein the brake rod is provided with a first flange, a second flange, a stop block and two springs, the two spring are located at both sides of the first flange and push against the mounting frame, the second flange and the stop block are located outside the mounting frame, the transmission shaft of the actuator has a limit block mounted on the brake rod and located between the second flange and the stop block.
 3. The limit switch device for an actuator as claimed in claim 2, wherein the stop block is screwed on the brake rod. 